The present invention relates to medico-surgical tubes and assemblies. The invention is more particularly concerned with cuffed medico-surgical tubes, such as, for example, cuffed tracheal tubes in which an inflatable cuff seals the tube with a patient's trachea.
For example, the conventional method of endotracheal intubation involves the insertion of a tubular device (an endotracheal tube) into the trachea. The endotracheal tube continues through the trachea and stops above the carina anterior to a position between the 2nd and 4th thoracic vertebrate, allowing the gases to be directed through the tube and into the lungs.
A primary objective of the treatment is the mechanical ventilation of the patient's lungs. This function normally induced by the patient's breathing, is typically impaired by the disease or injury being treated. In order to create the air pressure necessary to artificially ventilate the lungs, the passageway around the tube must be sealed. This is accomplished by a balloon or inflatable cuff provided around the tube. With the tube in place, the cuff is located about 3 to 5 centimeters above the carina and within the tube-like trachea.
The cuff is inflated to expand against the wall of the trachea and thereby to prevent gases that are being pumped into the lungs from simply backing up and escaping around the tube. This method of treatment has been quite successful for patients with chronic and acute respiratory disease. However, the method is not without complications.
Many intubated patients receiving the artificially induced ventilation may develop pneumonia. This pneumonia, known as Ventilator-Associated Pneumonia or VAP results from an infection of the lungs when pooled secretions, which have become infectious, are allowed, as a result of by-passing the upper airway, to enter the lungs. Unfortunately, this has been almost impossible to avoid with the prior endotracheal tubes.
The epiglottis is a form of valve that normally functions to selectively close the entry to the trachea and protect the airways (trachea and lungs) from secretions and particulate matter. The insertion of the endotracheal tube by-passes the protective system of the tracheo bronchial tree. Secretions that would normally be directed harmlessly through the digestive system follow the path of the tube, into the airway. The cuff above the carina blocks the downward flow of these secretions thus preventing them from entering the lungs. The secretions become pooled above the cuff and if unattended, rapidly grow infectious bacteria that pose a serious risk to the patient.
The problem of these prior endotracheal tubes arises primarily upon cessation of the mechanical ventilation. The cuff is deflated in order to withdraw the endotracheal tube from the trachea. The infected fluid is now released to continue passage down the trachea and into the highly susceptible lungs where bronchitis or pneumonia develops rapidly. Whereas deflation of the cuff in the presence of the pooled secretions poses the greatest threat of lung infection, there is substantial risk also during treatment, i.e. with the cuff inflated. An incomplete seal caused by folds or creases in the cuff is not unusual and fluids can and do migrate along them into the lungs. Though the se folds or creases are not typically a problem to the ventilation treatment, because they do allow microaspiration of the pooled secretions past the cuff it is desirable to remove the secretions and not allow them to accumulate for very long.
Various proposals have been made previously for removing such secretions by providing a suction aperture above the cuff. In Heyden U.S. Pat. No. 4,607,635 there is described a tracheal tube having a channel which opens at various locations along its length and through which a suction catheter can be inserted to remove secretions at any desired location above the cuff. In Chester U.S. Pat. No. 4,305,392 there is described a tracheal tube with a bulbous chamber above the cuff in which secretions are collected for removal through a suction lumen extending through the wall of the tube. The problem with both of these tubes is that it is not possible to remove secretions that collect immediately above the cuff. This is because the cuff is conventionally attached to the wall of the tube by means of short collars at opposite ends of the cuff, which are adhered to the tube and extend above and below the cuff. The length of the collar above the cuff defines the closest distance by which the suction aperture can be spaced from the cuff, because any attempt to form a suction aperture through the collar would weaken the joint between the cuff and the tube which might possibly lead to leakage from the cuff. In Porter U.S. Pat. No. 4,840,173 there is suggested a way in which secretions close to the cuff could be removed, by providing a suction tube which projects over the proximal collar of the cuff. This, however, would have the disadvantage of being relatively complex and expensive to make and may provide an undesirable projection from the side of the tube which could irritate the delicate surface of the trachea. There is also the risk that the end of the suction tube may damage the cuff or become blocked by the cuff. This risk can be reduced by making the upper end of the cuff more rigid, but this is a further complication in the construction of the tube.
What is needed is a means for removing secretions that collect immediately above the cuff that is simple, works with any cuff and does not negatively impact the trachea or the integrity of the cuff.